Contact lenses require frequent cleaning in order to remove deposits, the source of which is generally tear fluid. In addition to cleaning it is necessary to disinfect contact lenses to reduce the risk of infection. A common method of disinfecting contact lenses is to contact them with a three percent solution of hydrogen peroxide.
Prior art methods of disinfecting first clean and rinse the lenses and then immerse them in an aqueous three percent solution of hydrogen peroxide for about 20 minutes. The lens is then treated to reduce the residual hydrogen peroxide absorbed therein to a level which is non toxic and non irritating to the eye. In the prior art residual hydrogen peroxide has been reduced chemically by immersing the lens in an aqueous neutralizing solution followed by rinsing with isotonic saline. While neutralization has been accomplished in numerous ways in the prior art, one approach is to place the lenses in a container of saline solution having a plastic disc coated with catalytic platinum for about 4 hours. Other methods for neutralizing peroxide included immersion of the lens in an aqueous isotonic saline containing catalase or thiosulfate, or bisulfite and pyruvate salts and the like.
Another prior art method to reduce the residual peroxide employs multiple rinses and soaking with isotonic saline due to the high concentration (3%) of the peroxide employed in the disinfection step. Bausch and Lomb Quick Sept disinfection solution is of this type.
British patent number 2,144,875A (British '875) discloses a process for the oxidative cleansing of contact lenses which is similar to that utilized in cleansing dentures. An oxidative cleansing solution is prepared using a solid material which gives chemical release of hydrogen peroxide. Illustrative examples of solid materials giving chemical release of hydrogen peroxide include percarbonates, persulfates, perborates, peroxyhydrates and other per salts of alkali metals and other anions.
U.S. Pat. No. 4,414,127 discloses a method of utilizing a transition metal catalyzed peroxide solution to cleanse contact lenses. The preferred metal is copper.
U.S. Pat. No. 4,670,178 discloses a composition for simultaneously cleaning and disinfecting contact lenses which comprises a peroxide and a peroxide stable proteolytic enzyme. The peroxide concentration is such that the microbial load is reduced by one log order in three hours. At the lower end, this level is disclosed to be about 0.5% weight/volume peroxide. While there is no upper limit to peroxide concentration except as limited by the requirement that the enzyme retains proteolytic activity, the preferred range is about 1 to 2% (w/v) peroxide. Most preferably a solution of about 3% to about 10% (w/v) hydrogen peroxide is used. Although concentrations of peroxide as low as 0.02% (w/v) are disclosed and claimed, at those low levels the peroxide is disclosed as an activator for the enzyme and not as a disinfectant. The peroxide source can be hydrogen peroxide and its metal salts, alkali metal perborate monohydrate and tetrahydrate, alkali metal persulphates, alkali metal percarbonate peroxides, diperisophthalic acid, peroxydiphosphate salts and sodium aluminum aminohydroperoxide. The need to degrade unreacted peroxide is disclosed as part of the disinfecting/cleansing operation,
A lens disinfecting system available in Europe comprises a two solution system. The first solution for disinfecting the lens comprises 0.6% (w/v) of hydrogen peroxide together with cleaning additives. The second solution comprises a catalyst for deactivating residual peroxide. After treating the lens with the peroxide solution for a time to disinfect it, the lens is then soaked in the second solution for a time sufficient to deactivate residual peroxide.